Electrical Load Calculator — Domestic Property

This calculator lists common UK domestic appliances with their typical wattage ratings. You enter the quantity of each appliance in your property, and the calculator determines both the total connected load and the estimated maximum demand using diversity factors.

The calculation

Connected Load = Sum of (quantity × rated watts) for all appliances

Maximum Demand = Sum of (connected load × diversity factor) for all appliances

Current (Amps) = Watts ÷ 230V

Typical appliance wattages

• Kettle: 3,000W (diversity 10% — intermittent use)
• Oven: 3,000W (diversity 60% — not always at full power)
• Electric Hob: 6,000W (diversity 50% — rarely all rings at full)
• Washing Machine: 2,500W (diversity 30%)
• Electric Shower: 8,500-10,500W (diversity 100% — full load when on)
• Immersion Heater: 3,000W (diversity 100%)
• EV Charger: 3,600-7,000W (diversity 100% — continuous load)

The per-appliance diversity factors used here are simplified rule-of-thumb estimates based on typical domestic usage patterns — they are not taken from a published standard. BS 7671 itself does not list diversity values; the IET On-Site Guide (BS 7671:2018+A2:2022) Table A2 instead gives diversity allowances by circuit type (e.g. lighting 66%, cooking appliances first 10A + 30% of the remainder, socket circuits 100% of the largest + 40% of the rest, showers and immersion heaters at 100% with no diversity), while Table A1 gives the assumed current demands. The lighting figure (66%) used here is the one factor that matches Table A2. Actual usage varies — this calculator gives a reasonable estimate for supply sizing only.

For a circuit-by-circuit assessment that follows the IET On-Site Guide Table A2 diversity allowances exactly, use our Maximum Demand Calculator.